Polyurethane (PUR) and polyisocyanurate (PIR) foams are typically made from two component systems in which one component comprises an isocyanate and the other component comprises a polyol and/or other material reactive with the isocyanate. The two components are mixed under high or low pressure in the presence of a catalyst and blowing agent, with or without various additives. Representative of the mixers used in high pressure processes is the radial-flow, rotor-stator mixer, e.g., an OAKES mixer. Representative of mixers used in low pressure processes is the impingement mixer, e.g., an ELIMINATOR mixer.
“Froth foams” are blends that exit the applicator gun component of the mixer in a frothy state. This is in contrast to the “pour” foams which exit as a liquid and then cream and expand sometime after exiting the gun. Exiting the applicator gun as a froth allows for two important benefits to the end-user. One, the frothy foam will be resistant to leaking out of molds that have loose tolerances or other ‘leaky’ characteristics. Two, if there is enough frothing energy during material impingement in the gun, mixing from the gas expansion may be enough to give excellent polyol/isocyanate mixing without using a static mixer at the end of the applicator gun. Eliminating the static mixer is an advantage to the end-user because it frees the end-user from having to clean or flush the static mixer.
The typical froth blowing agent used in the United States is HFC-134a which is a gas at room temperature and has a zero ozone depletion. However, it has a high global warming potential (GWP). The direction of the marketplace and future legislation is towards low global warming potential blowing agents and away from high global warming potential blowing agents. A low-cost, low global warming potential gaseous blowing agent is very desirable for ‘froth’ foam end-users.